The present invention relates to a data transfer apparatus for transmitting/receiving, e.g., image data via communications, and its control method and, more particularly, to a data transfer apparatus of, e.g., an image processing device which outputs a large volume of data onto a communication path and must guarantee a given lower reduce of the data transfer rate like in a case wherein image data is transmitted to and printed by an electrophotographic printer, and its control method.
In recent years, high-speed serial communications such as IEEE1394 and the like begin to be used.
USB, IEEE1394, and the like comprise a mechanism for implementing data transfer with a data transfer rate guaranteed such as isochronous transfer mode. In isochronous transfer mode, since a required number of channels capable of data transfer are assured at prescribed cycle time intervals, a data transfer rate corresponding to the processing performance of a device is assured to transfer image data from an image scanning device to a computer or from the computer to an image forming device.
In high-speed serial communications such as IEEE1394, since the number of channels capable of data transfer in each prescribed cycle time interval is limited, if a given device has assured channels in such conventional image processing system, another device often fails to assure a required number of channels.